Method for forming a semiconductor

ABSTRACT

A preparing method of a semiconductor, particularly a preparing method of a polycrystal semiconductor film which has a good electrical property is disclosed. In order to obtain a non-crystalline silicon film containing a lot of combination of hydrogen and silicon, a forming process of a non-crystalline silicon film by a low temperature gas phase chemical reaction, a process of a heat annealing to produce a lot of dangling bonds of silicon, so as to draw out hydrogen from said non-crystalline silicon film, and a process of applying a laser irradiation to said non-crystal silicon film having a lot of dangling bond of silicon are conducted.

This application is a Continuation of Ser. No. 08/266,792, filed Jun.28, 1994 now abandoned; which itself is a continuation of applicationSer. No. 07/947,519, filed Sep. 21, 1992 now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for forming a semiconductor.Particularly, the present invention relates to a method for forming asemiconductor film, which has an excellent crystalline property andcontains less impurity in a crystalline film. The semiconductor filmprepared in accordance with the method of the present invention can beused in such semiconductor device as a high quality thin film transistorhaving a high field effect mobility.

2. Description of the Related Art

So far, a method for crystallization of a non-crystalline siliconhydride film formed by a plasma CVD or a heat CVD method, which containsa lot of hydrogen, and a lot of bonding hands of silicon which areneutralized with hydrogen (it can be described as a-Si : H), byirradiating such laser light as CW (Continuous-wave) laser and Excimerlaser has been well known.

This method, however, poses a problem that a non-crystalline siliconfilm as a starting film contains a lot of hydrogen, much of which spoutsfrom the film when the film is subjected to a laser irradiation, andthen a film quality deteriorates remarkably. To overcome this problem,there have been used chiefly the following three methods.

(A) At first, by irradiating a low energy density (less than thresholdvalue energy for crystallization) laser light to a non-crystallinesilicon hydride film as a sample, hydrogen in the starting film as asample will be draw out. And then, by irradiating a high energy densitylaser light to the sample, the sample will be crystallized. This iscalled as a multi-stage irradiation method.

(B) By forming a non-crystalline silicon hydride film, at 400° C. ormore of a substrate temperature, a hydrogen content in the starting filmwill be decreased. Thus, a film quality deterioration by a laserirradiation will be prevented.

(C) By effecting a heat treatment of a non-crystalline silicon hydridefilm, in an inactive atmosphere, hydrogen in the film will be removed.

The following problems, however, have been posed, in order to obtain ahigh quality crystal film (in general, polycrystal silicon film) by theabove mentioned methods.

(1) The method of (A) has a problem in a practical use. Namely, it isbad in an efficiency of hydrogen drawing out, difficult to control alaser energy output, and required to increase the number of laserirradiation times. Since almost all the laser light energy is absorbedin the film surface, it is difficult to draw out hydrogen, in case of athick film.

(2) The method of (B) has a problem that a crystallization is obstructedin a later process of crystallization by a laser light. This is causedby that an impurity content in the film is inclined to increase, when asubstrate temperature becomes high, and a silicon cluster (microcrystalpart of silicon) is formed, if a non-crystalline silicon hydride film isformed at a high temperature.

(3) The method of (c) has a problem that an electric property (carriermobility etc.) of the crystal film deteriorates, caused by such impurityas oxygen. This is derived from the reason that since hydrogen iseliminated by heating, a dangling bond (unpaired bonding hand) ofsilicon is formed, and the dangling bond combines easily with oxygenetc. then, the oxygen intrudes easily into the film from its surface to10 to 20 nm in depth, and diffuses into the film deeply by a hightemperature diffusion.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to solve the abovementioned problems. The object can be accomplished by adopting a methodfor forming a semiconductor in accordance with the present invention.Such a method in accordance with the present invention is describedbelow (a) to (c).

(a) A non-crystalline (amorphous or microcrystal) silicon hydride filmhaving a Si--H bond of high density is formed on a substrate, at a lowtemperature by a gas phase chemical reaction (chemical vapordeposition). As a method of the gas phase chemical reaction, suchconventional method as a plasma CVD (chemical vapor deposition) method,a heat CVD (thermal chemical vapor deposition) method, and a light CVD(photo chemical vapor deposition) method can be employed. At this time,it is needed to form a non-crystalline (amorphous or microcrystal)silicon hydride film at 350° C. or lower of a substrate temperature,which is said to be an eliminating temperature of hydrogen from thenon-crystalline (amorphous or microcrystal) silicon hydride. This is toincrease the number of bond between silicon and hydrogen (Si--Hbonding), by making hydrogen contain in a film as much as possible, in afilm forming process. It is preferable to form a film at a substratetemperature as low as possible, in order to maximize Si--H bonding.However, in an actual use, it is possible to achieve the maximizingobject of Si--H bonding, by forming a film at 100° to 200° C. of thesubstrate temperature.

Also, it is possible to prevent a silicon cluster (microcrystal ofsilicon) from being formed in a film, by effecting a film forming at alow temperatures and to expect a more uniform crystallization, at alater crystallizing process.

(b) Hydrogen in a non-crystalline (amorphous or microcrystal) siliconfilm is expelled from the silicon film and a high density dangling bondis formed in silicon, by effecting a heat treatment (thermal annealing)of the non-crystalline (amorphous or microcrystal) silicon film, whichwas formed in the above mentioned (a) process, in a vacuum or inactivegas atmosphere. The heat treatment in a vacuum or inactive gasatmosphere comes from that a combination (bonding) of the dangling bondof silicon and such impurity as oxygen is prevented to the utmost. It isimportant for the heating temperature that the substrate temperature be350° C. or higher and also 500° C. or lower. This is based on that theeliminating temperature of hydrogen from a non-crystalline (amorphous ormicrocrystal) silicon hydride is about 350° C., and the crystallizationstarting temperature of a non-crystalline (amorphous or microcrystal)silicon is about 500° C. Also, since there is a case where thecrystallization starts at 450° C., when an impurity concentration,especially oxygen in the film is low, it is preferable that this heatingprocess to draw out hydrogen is carried out at 400° C. extent in anactual use. It is suitable that the time for the heating process is inthe degree of 30 min. to 6 hrs. The inactive gas atmosphere comprises amaterial selected from the group consisting of N₂, Ar, H₂, He and amixture thereof. In case of the inactive gas atmosphere, the heatedamorphous or microcrystal film is irradiated with the laser lightthrough a cap layer provided on the heated amorphous or microcrystalfilm. Pressure of the inactive gas atmosphere is e.g. 0.5 atm. to 1.5atm.

This heating process is to be carried out, so as to produce a lot ofdangling bond, by releasing hydrogen made be contained in anon-crystalline (amorphous or microcrystal) silicon in the above (a)process. Moreover, this producing a lot of dangling bond is to make thecrystallization easy, in a later crystallizing process by a laserirradiation or heating. So that it is not preferable that thenon-crystalline (amorphous or microcrystal) silicon film crystallizes inthis heat treatment step. The reason why the crystallization (includinga cluster state in the very small region) in this heat treatment stepshould be avoided is based on the fact that once crystallized film willnot give a good quality in an electric performance, on the contrary, itwill deteriorate, even if an energy for the crystallization (e.g.irradiation energy of laser) is added.

Also, afterward, there is a crystallizing process for non-crystalline(amorphous or microcrystal) silicon film by a laser irradiation or aheating. But, it is very effective in the improvement of filmcrystalline property in a crystallizing process by the later laserirradiation or the heating, to maintain an atmosphere in a vacuum orinactive state and to avoid a combination (bonding) of impurity with thedangling bond of film to the utmost, up to this crystallizing process.

(c) A non-crystalline (amorphous or microcrystal) silicon film iscrystallized by a laser irradiation or a heating with the vacuum orinactive gas atmosphere maintained. In this process, it is extremelyimportant not to break the vacuum state or inactive gas atmosphere insuccession with the above (b) process. This results from the reason thatsilicon in the non-crystalline silicon film is apt to react withimpurity exceedingly, as a dangling bond has been formed with highdensity in the non-crystalline (amorphous or microcrystal) silicon filmduring the heating (thermal annealing) process (b). The non-crystalline(amorphous or microcrystal)silicon film is maintained in a vacuum orinactive gas atmosphere from the process (b) to the process (c). Thenon-crystalline (amorphous or microcrystal) silicon film is irradiatedwith a laser light or heated at a temperature of 500° C. or higher inthe process (c). The process (c) is carried out after the process (b).

Also, it is effective in the improvement of crystalline property toapply a laser irradiation to a substrate, heating it at about 300° C. to500° C., so as to lower a cooling speed of the substrate temperature, atthis occasion. In case of the crystallizing by only heating, it can beeffected by heating at a temperature of 450° C. or higher, typically450° C. to 800° C., but in general, it is conducted by heating at 600°C. degree for 1 hr. to 96 hrs. considering a heat-resistant temperatureof a glass substrate.

In the claim of the present invention, it is defined that anon-crystalline (amorphous or microcrystal) silicon starts oncrystallization at 500° C. or higher. But, it starts on it at the degreeof 450° C. if an oxygen concentration in a film is very low. Therefore,it is defined as such.

In the present invention, it is important to form a non-crystalline(amorphous or microcrystal) silicon hydride film which has high densitybonds between silicon and hydrogen, as a starting film, and to obtain anon-crystalline (amorphous or microcrystal) silicon film having a highdensity dangling bond, drawing out hydrogen from the starting film,through the heat annealing process to accelerate a dehydrogenation fromthe film. The employment of such film is due to the fact that the filmhas a tendency to crystallize, as a non-crystalline silicon film havinga high density dangling bond of silicon is active in a lattice vibrationof an atom level, and is in a very unstable condition thermally. Andthen, a polycrystal silicon semiconductor film is obtained bycrystallizing the noncrystalline (amorphous or microcrystal) siliconfilm, which has been apt to crystallize, after the dangling bond wasformed with high density, by a laser irradiation and a heating for thecrystallization.

Also, it is important to maintain the non-crystalline (amorphous ormicrocrystal) silicon semiconductor film in an atmosphere isolated fromthe open air, in the above mentioned process, i.e. from the film forming(film deposition) process (a) to the crystallization process (c) throughthe heating process (b). This is to prevent the dangling bond fromcombining with oxygen etc. to the utmost. And in order to attain thisobject, an equipment having a chamber, which is provided with a highvacuum exhaust system, a quartz window for laser irradiation, a heatingapparatus for heating process and the like, is needed. In an industrialscale, a multi-chamber type equipment provided with the above mentionedapparatus or device is useful.

BRIEF DESCRIPTION OF THE DRAWING

The objects, features, and advantages of the present invention willbecome more apparent, from the following description of the preferredembodiment taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 shows a preparing process diagram of the insulating gate thinfilm type field effect transistor (hereinafter referred to as TFT)obtained according to Example 1.

FIG. 2 shows an another preparing process diagram of TFT obtainedaccording to Example 1.

FIG. 3 shows a still another preparing process diagram of TFT obtainedaccording to Example 1.

FIG. 4 shows a further preparing process diagram of TFT obtainedaccording to Example 1.

FIG. 5 shows a still further preparing process diagram of TFT obtainedaccording to Example 1.

FIG. 6 shows a schematic diagram of the vacuum chamber used in Example1.

FIG. 7 is a graph showing the electric property of TFT obtainedaccording to Example 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will be explained in more detail by reference tothe following Examples, in connection with the drawings. The presentinvention is by no means limited to the Examples.

EXAMPLE 1

Here is shown an n-channel type thin film insulated gate field effecttransistor, which uses the polycrystal silicon (poly-Si) prepared inaccordance with the present invention. Also in the present Example, anexcimer laser (KrF, wave length 248 nm) was used as a crystallizingmeans.

FIGS. 1 to 5 show the preparing process diagrams of TFT (thin filminsulated gate field effect transistor) obtained in accordance with thepresent Example. In the present Example, a glass or a quartz substratewas used as a substrate. This is due to the aim that the TFT prepared inthe present Example will be used as a switching device or a drivingdevice of an active matrix type liquid crystal display device or animage sensor. However, in case where the present invention is used inthe other semiconductor device, as a substrate, a single crystal or apolycrystal of silicon may be used, and other insulating material may beused.

In FIG. 1, SiO₂ film or silicon nitride film was formed on a glasssubstrate 11, as a base protective film 12. In the present Example, SiO₂film 12 was formed in 200 nm thick, by RF sputtering in an atmosphere of100 % oxygen. The film forming condition was as follows: 0₂ flow amount;50 sccm, Pressure; 0.5 pa, RF electric power; 500 W, and Substratetemperature; 150° C.

Next, an intrinsic or a substantially intrinsic (which is meant by thatan impurity is not added artificially) noncrystalline (amorphous ormicrocrystal)silicon hydride semiconductor layer 13 was formed in 100 nmthick, by a plasma CVD method. A channel forming region will be formedin this layer 13. The film forming condition was as follows: Atmosphere;100 % of silane (SiH₄), Film forming temperature; 160° C. (substratetemperature), Film forming pressure; 0.05 Torr, and Making power; 20 W(13.56 MHz). In the present Example, as a film forming material gas of anon-crystalline (amorphous or microcrystal) silicon, silane was used.But in case where a non-crystalline (amorphous or microcrystal) siliconis made be polycrystallized by a heat crystallization, disilaneespecially trisilane may be used in order to lower the crystallizationtemperature.

To conduct the film forming in an atmosphere of 100 % silane was basedon the experimental result that the non-crystalline (amorphous ormicrocrystal) silicon film formed in said atmosphere was more inclinedto crystallize, compared with the one formed in such conventionalatmosphere as the atmosphere of silane diluted with hydrogen. To effectthe film forming at the low temperature was resulted from reason that abonding hand of silicon would be neutralized as much as possible withhydrogen, by making a lot of hydrogen contain in the formednon-crystalline (amorphous or microcrystal) silicon film.

Also, the application of the low making power of a high frequency waveenergy (13.56 MHz) such as 20 W was to prevent the film from beingarisen of a silicon cluster i.e. a part having crystal, in the filmforming process to the utmost. This was also based on the experimentalresult that if even a little of crystalline part was contained in thenon-crystalline (amorphous or microcrystal) silicon film, it gave a badinfluence on the crystallization in the later laser irradiation process(it gave an irregular crystallization).

Next, a device separation patterning was carried out to get a shapeshown in FIG. 1. Then, a high density dangling bond was formed in thefilm, drawing hydrogen thoroughly from the film, by heating the sampleat 450° C. for an hour in a vacuum (10⁻⁶ Torr or less). Further, thecrystallization of sample was effected, by an excimer laser irradiation,keeping a vacuum condition in the chamber in which the aforesaidhydrogen drawing out was conducted. The process condition using a KrFexcimer laser (wave length 248 nm) was as follows: Laser irradiationenergy density; 350 mJ/cm², Pulse No.; 1 to 10 shot, and Substratetemperature; 400° C. After the finishment of laser irradiation, thetemperature was lowered to 100° C. in hydrogen reduced atmosphere (about1 Torr).

In the present Example, the above heating process for hydrogen drawingout from the sample and the crystallization by an excimer laserirradiation was executed, using the same vacuum chamber as shown in FIG.6. By using such vacuum chamber, it is possible to make it easy tomaintain vacuum condition, covering from the heating process to thecrystallizing process by a laser irradiation, and to obtain a film intowhich an impurity (especially oxygen) is not mixed. Of course, theprocesses from the film forming to the laser irradiation may be effectedin succession, without a transfer of sample, by using such plasma CVDapparatus as is provided with a high vacuum exhausting device and have awindow of quartz etc. so that a laser can be irradiated from theoutside, instead of the chamber exclusively used in the laser annealing.

In FIG. 6, the numerals are as follows: 21; Vacuum chamber, 22; Quartzwindow for irradiation of laser from the outside of vacuum chamber 21,23; Laser light when laser was irradiated, 24; Sample, 25; Sampleholder, 26; Heater for sample heating, and 27; Exhausting system, inwhich a rotary pump for a low vacuum, and a turbo molecular pump for ahigh vacuum were used, and it was tried to reduce a remainedconcentration of an impurity (especially oxygen) in the chamber to theutmost.

After crystallization by an excimer laser, using the vacuum chamber ofFIG. 6, SiO₂ film was formed in 50nm thick by RF sputtering method, onlygate region of which was patterned utilizing a photoresist to form aninsulating film 15. This insulating film was so provided that a channelforming region thereof was protected not to be contaminated with animpurity (especially oxygen). Also, the photoresist 16 on the insulatingfilm 15 made be remained without being removed, and a channel formingregion was formed beneath this insulating film (gate insulating film)15.

Then, an n⁺ -type non-crystal silicon film 17 to be a source and a drainregion was formed in 50nm thick, by a plasma CVD method under thecondition described below:

Film forming atmosphere; H₂ : SiH₄₌ 50: 1 (1 % of PH₃ was added);Substrate temperature; 150 to 200° C. Film forming pressure; 0.1 Torr,and Making power; 100 to 200 W. As to the film forming, it is preferableto form a film holding the temperature at 200° C. or lower, so that theresist will not harden by heat. Also, here, P-channel type TFT can beobtained, by adding an impurity (e.g. B₂ H₆ is used) which gives P-typeconductivity. Under these situation, the shape of FIG. 2 was obtained.Then, an n⁺ type non-crystalline (amorphous or microcrystal) siliconfilm was removed from on a gate region by a lift off method to obtainthe shape of FIG. 3. This is a method to remove a film formed in thecircumference and on this photoresist (in this case, n⁺ -typenon-crystal silicon film) along with a photoresist, by removing theremained photoresist at the same time.

Further, as indicated by an arrow in FIG. 3, an energy was given to n⁺-type non-crystalline (amorphous or microcrystal) silicon film to becomea source and drain region (171 and 172), by irradiation of KrF excimerlaser, and the source, drain region was activated (activation of animpurity which was contained in source, drain region and gives oneconductivity type). At this time, the laser irradiation condition by KrFexcimer laser (248 nm) was below:

Energy density; 250 mJ/cm², Pulse No.; 10 to 50 shots, and Substratetemperature; 350° C. Of course, here, it is needless to say that a laserexcept the KrF excimer laser can be used.

After the above process was over, the sheet resistance of n⁺ -typenon-crystalline silicon film to become a source, drain region waslowered to the degree of 100 to 200 Ω/cm². Also, silicon oxide film 15,the protective film which protected a channel forming region (regionunder 15) was removed.

After the above activation of the source, drain region, SiO₂ film 18 wasformed in 100 nm thick by RF sputtering method, as shown in FIG. 4. Thefilm forming condition was the same with the preparation method of agate oxide film.

Then, the openings for contacts were formed by patterning to obtain theshape of FIG. 4. Further, aluminum for an electrode was vapor depositedand the wirings and electrodes were formed by patterning. After that,hydrogen annealing was executed, in hydrogen atmosphere of 350° C. tofinish a device.

FIG. 7 is a graph showing a characteristic of I_(D) -V_(G) of TFTprepared according to the present Example. In FIG. 7, I_(D) is draincurrent, and V_(G) is gate voltage. Also, the cases of 10 V and 1 V ofdrain voltage are shown.

The comparative data between the various characteristics of TFT preparedaccording to the present Example, and TFT obtained by the conventionalpreparing method are shown in the Table 1.

Comparative Example

The different point between Example 1 and Comparative Example was thatin Example 1, the vacuum condition was maintained, throughout theprocesses from the heating for hydrogen drawing out to the laserirradiation for crystallization. To the contrary, in the ComparativeExample, the different chambers were used respectively with respect tothe above processes of Example1. Then, the sample surface, i.e. thesurface of non-crystalline silicon semiconductor film was exposed to theopen air, when the sample was moved from the heating furnace, in whichthe heating for hydrogen drawing out was effected, to the vacuum chamberto apply a laser irradiation. Other preparing process conditions werethe same with Example 1. It can be therefore understood that bycomparing this Comparative Example with Example 1, how it is importantto maintain the vacuum atmosphere in the processes from hydrogen drawingout to the crystallization, in relation to the present invention inwhich high density dangling bond will be formed, by drawing outhydrogen.

The Table 1 shows the electrical properties of Example 1 and thisComparative Example. From the Table 1, it is evident that Example 1 issuperior to Comparative Example, in all respects of Field EffectMobility, ON/OFF Current Ratio, Threshold Value Voltage, and S Value.

                  TABLE 1                                                         ______________________________________                                        Field Effect  ON/OFF Current                                                                            Threshold                                           Mobility      Ratio       Value Voltage                                                                            S Value                                  ______________________________________                                        Example 1                                                                             329 cm.sup.2 /Vs                                                                        7.6 × 10.sup.7                                                                      3.7 V    0.37                                   Comparative                                                                            61 cm.sup.2 /Vs                                                                        7.8 × 10.sup.5                                                                      4.8 V    0.57                                   Example                                                                       ______________________________________                                    

The Field Effect Mobility in the Table 1 is an index showing a speedthat a carrier crosses a channel, and it indicates that the bigger thisvalue is, the higher switching speed and operation frequency are.

ON/OFF Current Ratio is defined as a ratio of the ID value in case ofV_(D) =1(V), V_(G) =30(V) and the minimum I_(D) value of I_(D) -V_(G)curve (shown in FIG. 7) in the same case. It indicates that the biggerthis ON/OFF Current Ratio is, the less leak current in case of OFF timeis, which shows an excellent switching device.

Threshold Value Voltage indicates that the lower this value is, the lesscurrent consumption is. In case of an active matrix type liquid crystaldisplay device, which is required to drive hundred thousands of TFT, itis important problem that the Threshold Value Voltage is low.

S Value is a minimum value of (d(I_(D))/d(V_(G)))-1 in the rising partof curve, in the graph showing a relationship of gate voltage (V_(G))and drain current (I_(D)) as shown in FIG. 7, and it indicates aparameter representing a steepness of I_(D) -V_(G) curve. It isappreciated that the less this S Value is, the more excellent device ina switching property is.

As mentioned in the above, it is understood that a high characteristicTFT can be prepared in accordance with the present invention. At thesame time, it is also understood that a polycrystal siliconsemiconductor which is excellent in an electrical quality can beobtained. In particular, it is apparent that the shifting from theheating process for drawing out of hydrogen to the crystallizing processkeeping a vacuum condition is important, in contrast to the ComparativeExample.

It is needless to say that TFT obtained by the present Example can beapplicable to a switching device of a liquid crystal display device aswell as an integrated circuit device. Also, the present invention is notlimited to a structure of TFT obtained by the present Example, but isavailable to a preparing method of TFT which forms a source, drainregion, by an ion implantation in a self-alignment method.

EXAMPLE 2

According to this Example, in the TFT prepared in Example 1, thecrystallization was carried out by a heating. The heating temperatureand the heating time for the crystallization were 600° C. and 48 hrs.respectively.

Also, according to this Example, the device separation patterningconducted in the Example 1 was executed after the crystallization byheating. Namely, after a non-crystalline (amorphous or microcrystal)silicon intrinsic or substantially intrinsic (it is meant by that animpurity is not made be mixed artificially) semiconductor film to becomea channel region, in which there existed high-densely bonds betweensilicon and hydrogen, was formed, hydrogen was drawn out at thetemperature of from 350° C. to 500° C. (at 450° C. or less in case oflow oxygen content in a film ), maintaining a vacuum condition withoutbeing exposed to the open air, and then, a crystallization was carriedout, at the temperature of 600° C. maintaining the vacuum condition asit was in succession. After that, a device separation patterning wasexecuted.

The heating process for the hydrogen drawing out was conducted at 400°C. for an hour, and the heating process for crystallization wasconducted at 600° C. for 48 hrs. Other processes were conducted inaccordance with the same processes as those in Example1. Also in thisExample, a lot of dangling bonds were formed, drawing out hydrogen fromthe non-crystalline (amorphous or microcrystal) silicon film, which wasobtained by combination of an excess hydrogen with silicon, and then, itwas important that the heating for a crystallization was effected, bykeeping the non-crystalline (amorphous or microcrystal) silicon film, inwhich a lot of these dangling bonds existed, in a vacuum condition.

In the above explanation, it is mainly referred to silicon, but thepresent invention is useful for the cases where other non-crystalline(amorphous or microcrystal) semiconductor film is crystallized. Also, itis needless to say that the polycrystal semiconductor film preparedaccording to the present invention can be applied to a photoelectricconversion device or other semiconductor device.

In accordance with the present invention, by conducting the followingprocess steps, a polycrystal silicon semiconductor film having anexcellent electrical property can be obtained, and it has becomeapparent that TFT using this polycrystal silicon semiconductor film hasa remarkable characteristics.

(a) preparing a non-crystalline (amorphous or microcrystal) siliconhydride film at low temperature, and producing a lot of Si-H bondings insaid film,

(b) applying a heat treatment in a vacuum to said non-crystalline(amorphous or microcrystal) silicon hydride film prepared in the (a)process, and dehydrogenating it to produce a lot of dangling bonds, and

(c) applying an excimer laser irradiation in a vacuum as such in the (b)process, or applying a heat treatment for a crystallization.

What is claimed is:
 1. A method for forming a semiconductor comprisingthe steps of:annealing a non-single crystalline silicon film comprisingbonds between silicon and hydrogen formed on a substrate in a vacuum orinactive gas atmosphere to produce dangling bonds therein with hydrogensof said bonds between silicon and hydrogen expelled therefrom; andirradiating a laser light to the annealed non-single crystalline siliconfilm containing said dangling bonds therein with said vacuum or inactivegas atmosphere maintained to crystallize said annealed non-singlecrystalline silicon film into a crystalline silicon semiconductor film,wherein said non-single crystalline silicon film is deposited through aplasma CVD using a 100% silane as a reactive gas.
 2. The method of claim1 wherein said vacuum is at a pressure of 10⁻⁶ Torr or less.
 3. Themethod of claim 1 wherein said annealed non-single crystalline film isirradiated with said laser light through a cap layer provided on saidannealed non-single crystalline silicon film.
 4. The method of claim 1wherein the step of thermally annealing is performed at a temperaturesufficiently low not to initiate a crystallization of said film.
 5. Amethod for forming a semiconductor comprising the steps of:depositing anon-single crystalline film comprising silicon on a substrate; firstheating said non-single crystalline film at a temperature of 350° C. to500° C.; and second heating said non-single crystalline film at atemperature of 500° C. or higher after said first heating step, whereinsaid non-single crystalline film is maintained in an atmosphere isolatedfrom air during said depositing step and said first and second heatingsteps and is maintained in a vacuum or inactive gas atmosphere duringsaid first and second heating steps, and wherein said non-singlecrystalline film is deposited through a plasma CVD using a 100% silaneas a reactive gas.
 6. The method of claim 5 wherein said annealednon-single crystalline film comprises hydrogen.
 7. The method of claim 5wherein the deposition of said non-single crystalline film is carriedout at a temperature of 350° C. or lower.
 8. The method of claim 5wherein said annealed non-single crystalline film is maintained in saidinactive gas atmosphere and said inactive gas atmosphere comprises amaterial selected from the group consisting of N₂, Ar, H₂, He and amixture thereof.
 9. The method of claim 5 wherein said depositing stepis carried out by plasma chemical vapor deposition, thermal chemicalvapor deposition or photo chemical vapor deposition.
 10. The method ofclaim 5 wherein said non-single crystalline film as deposited comprisesSi--H bond.
 11. The method of claims 1 or 5 wherein said semiconductoris a channel semiconductor layer of an insulated gate field effecttransistor.
 12. The method of claim 5 wherein the temperature at whichsaid first heating is performed is sufficiently low to avoid thecrystallization of said film.
 13. The method of claim 12 wherein saidfilm is crystallized by said second heating step.
 14. A method formanufacturing a thin film transistor having at least a channelsemiconductor layer, gate insulating layer and a gate electrode, saidmethod comprising the steps of:forming a non-single crystallinesemiconductor layer on a surface of a substrate; heat treating saidsemiconductor layer in order to discharge hydrogen contained in saidlayer at a low temperature so as to not initiate a crystallization ofsaid semiconductor layer; and irradiating the heat treated semiconductorlayer with light in order to crystallize said semiconductor layer,wherein said non-single crystalline semiconductor layer is depositedthrough a plasma CVD using a 100% silane as a reactive gas.
 15. Themethod of claim 14 wherein the steps of forming said semiconductorlayer, heat treating and irradiating are successively carried outwithout exposing said semiconductor layer to air.
 16. A method of claim1, 5 or 14 wherein said CVD is plasma CVD.
 17. A method of claim 14wherein said thin film transistor is an image sensor.
 18. A method ofclaim 14 wherein said thin film transistor is an active matrix liquidcrystal device.
 19. A method for manufacturing a semiconductor devicecomprising the steps of:depositing an amorphous semiconductor filmcomprising silicon over a substrate through CVD using a reactive gas;and crystallizing said amorphous semiconductor film by heating, whereinsaid reactive gas comprises 100% silane.
 20. A method of claim 19wherein said silane is selected from the group consisting of disilaneand trisilane.
 21. A method of claim 19 further comprising a step ofdehydrogenating said amorphous semiconductor film after the depositionthereof.
 22. A method of claim 19 wherein said semiconductor device isan image sensor.
 23. A method of claim 19 wherein said semiconductordevice is an active matrix liquid crystal display device.
 24. A methodof claim 19 wherein said CVD is a plasma CVD.
 25. A method of claim 19wherein said substrate is a quartz.